The present invention in general relates to compass saws.
More particularly, it relates to a compass saw which has a base plate and a lifting rod for receiving a saw blade as well as a guiding sword forming support means.
Compass saws of the above mentioned general type are known in the art. One of such compass saw is disclosed in U.S. Pat. No. 1,940,483. In this patent a textile cutting machine operates as a compass saw and has a reciprocating cutter with a back supported in a guide formed as a sliding rail. The guide is arranged between the housing of the textile cutting machine and its base plate. Similarly to the cutter, the does not project under the base surface of the base plate.
The German patent document DE-OS 41 04 296 discloses a compass saw of the same type. In this reference the compass saw has a sword which is fixed with the housing under a base plate and formed as a tongue in alignment with the saw blade. The sword operates for receiving a second base plate which is displaceable along the sword and extends parallel to the first base plate. The base plate is fixed on the sword. This sword first of all forms a support for the second base plate and, together with the second base plate, adds a relatively high additional weight to the compass saw. Moreover, for works during which the sword and the second base plate are needed, the mounting expense for removing these parts is substantially high.
The textile cutting machine has the disadvantage that the sword is suitable only for guidance of the compass saw blades above the base plate. The known compass saw has the disadvantage that either the available sword must be used always during sawing, or a complicated, time-consuming dismounting of the sword must be taken into consideration for the cases when a sawing without sword is advantageous.
Another disadvantage of the known compass saws is the rigid arrangement of the sword so that during swinging compass sawing the saw blade back is supported only temporarily and is not supported in particular during the swinging sword of the saw blade in the feed direction. The saw blade back moves away from the sword when a stabilization of the saw blade during engagement in the workpiece must be most efficient and is needed the most.
The operational results with the known saw blades having the guiding sword are only significantly better than for the saw blades without the guiding sword.